Method for large scale manufacture of thin film photovoltaic devices using multi-chamber configuration

ABSTRACT

A method for large scale manufacture of photovoltaic devices includes loading a substrate into a load lock station and transferring the substrate in a controlled ambient to a first process station. The method includes formation of a first conductor layer overlying the surface region of the substrate. The method includes transferring the substrate to a second process station, and forming a second layer overlying the surface region of the substrate. The method further includes repeating the transferring and processing until all thin film materials of the photovoltaic devices are formed. In an embodiment, the invention also provides a method for large scale manufacture of photovoltaic devices including feed forward control. That is, the method includes in-situ monitoring of the physical, electrical, and optical properties of the thin films. These properties are used to determine and adjust process conditions for subsequent processes.

CROSS-REFERENCES TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.13/179,719 filed on Jul. 11, 2011, which is a division of U.S. patentapplication Ser. No. 12/269,768 filed on Nov. 12, 2008, which claimspriority to (a) U.S. Provisional Application No. 60/988,089 filed Nov.14, 2007 and (b) U.S. Provisional Patent Application No. 60/988,099,filed Nov. 14, 2007, the contents of all the above applications areincorporated by reference herein in their entirety for all purposes.

This application is also related to (a) U.S. patent application Ser. No.11/748,444, filed May 14, 2007, (b) U.S. patent application Ser. No.11/804,019, filed May 15, 2007, and (c) U.S. patent application Ser. No.13/179,722, filed Jul. 11, 2011, all of which are commonly assigned andincorporated by reference herein in their entirety for all purposes.

BACKGROUND

The present invention relates generally to photovoltaic materials. Moreparticularly, the present invention provides a method and system forlarge scale manufacture of multi junction and single junction solarmodules using integrated manufacturing systems for thin and thick filmphotovoltaic materials. Merely by way of example, the present method andstructure have been implemented using a solar module having multiplethin film materials, but it would be recognized that the invention mayhave other configurations.

From the beginning of time, human beings have been challenged to findway of harnessing energy. Energy comes in the forms such aspetrochemical, hydroelectric, nuclear, wind, biomass, solar, and moreprimitive forms such as wood and coal. Over the past century, moderncivilization has relied upon petrochemical energy as an importantsource. Petrochemical energy includes gas and oil. Gas includes lighterforms such as butane and propane, commonly used to heat homes and serveas fuel for cooking Gas also includes gasoline, diesel, and jet fuel,commonly used for transportation purposes. Heavier forms ofpetrochemicals can also be used to heat homes in some places.Unfortunately, petrochemical energy is limited and essentially fixedbased upon the amount available on the planet Earth. Additionally, asmore human beings begin to drive and use petrochemicals, it is becominga rather scarce resource, which will eventually run out over time.

More recently, clean sources of energy have been desired. An example ofa clean source of energy is hydroelectric power. Hydroelectric power isderived from electric generators driven by the force of water that hasbeen held back by large dams such as the Hoover Dam in Nevada. Theelectric power generated is used to power up a large portion of LosAngeles Calif. Other types of clean energy include solar energy.Specific details of solar energy can be found throughout the presentbackground and more particularly below.

Solar energy generally converts electromagnetic radiation from our sunto other useful forms of energy. These other forms of energy includethermal energy and electrical power. For electrical power applications,solar cells are often used. Although solar energy is clean and has beensuccessful to a point, there are still many limitations before itbecomes widely used throughout the world. As an example, one type ofsolar cell uses crystalline materials, which form from semiconductormaterial ingots. These crystalline materials include photo-diode devicesthat convert electromagnetic radiation into electrical current.Crystalline materials are often costly and difficult to make on a widescale. Additionally, devices made from such crystalline materials havelow energy conversion efficiencies. Other types of solar cells use “thinfilm” technology to form a thin film of photosensitive material to beused to convert electromagnetic radiation into electrical current.Similar limitations exist with the use of thin film technology in makingsolar cells. That is, efficiencies are often poor. Additionally, filmreliability is often poor and cannot be used for extensive periods oftime in conventional environmental applications. There have beenattempts to form heterojunction cells using a stacked configuration.Although somewhat successful, it is often difficult to match currentsbetween upper and lower solar cells. These and other limitations ofthese conventional technologies can be found throughout the presentspecification and more particularly below.

From the above, it is seen that improved techniques for manufacturingphotovoltaic materials and resulting devices are desired.

SUMMARY

The present invention relates generally to photovoltaic materials. Moreparticularly, the present invention provides a method and system forlarge scale manufacture of multi junction and single junction solarmodule using integrated manufacturing system and method for thin andthick film photovoltaic materials. Merely by way of example, the presentmethod and structure have been implemented using a solar module havingmultiple thin film materials, but it would be recognized that theinvention may have other configurations.

According to a specific embodiment, the invention provides system formanufacturing a photovoltaic device. The system includes a first loadlock station and a second load lock station. The system also includes aplurality of process stations arranged in a serial configuration betweenthe first and the second load lock stations. The plurality of processstations numbered from 1 through N, where N is an integer greater than2. In a specific embodiment, the system includes a transfer stationcoupled between two adjacent process stations.

According to another embodiment, the invention provides a system formanufacturing a photovoltaic device. The system includes a load lockstation and a plurality of process station. Each of the plurality ofprocess stations being coupled to the load lock station. In a specificembodiment, the system also includes a transport station coupled betweena first process station and the load lock station.

According to other embodiments of the invention, various methods areprovided for large scale manufacture of photovoltaic devices. In aspecific embodiment, the method includes loading a substrate into a loadlock station and transferring the substrate in a controlled ambient to afirst process station. The method includes using a first physicaldeposition process in the first process station to cause formation of afirst conductor layer overlying the surface region of the substrate. Themethod includes transferring the substrate to a second process station,and using a second physical deposition process in the second processstation to cause formation of a second layer overlying the surfaceregion of the substrate. The method further includes repeating thetransferring and processing until all thin film materials of thephotovoltaic devices are formed.

In another embodiment, the invention also provides a method for largescale manufacture of photovoltaic modules including feed forwardcontrol. That is, the method includes in-situ monitoring of thephysical, electrical, and optical properties of the thin films. Theseproperties are used to determine or adjust process conditions forsubsequent processes.

In an alternative embodiment, the present invention provides a systemfor large scale manufacture of thin film photovoltaic modules. Thesystem includes a plurality of chambers configured to hold a substratesubjecting one or more thin film processes for manufacture of a thinfilm photovoltaic module. The substrate is optically transparent and hasa lateral dimension of 1.5 meter and greater. The system furtherincludes one or more load locks coupling to the plurality of chambersfor loading the substrate into/out of each chamber. Additionally, thesystem includes a transfer tool configured to transfer the substrateinto/out of each of the plurality of chambers via at least one of theone or more load locks. Embodiments of the invention provide that atleast some of the plurality of chambers are configured to form acopper-indium composite material with Cu-rich stoichemistry in terms ofa Cu:In ratio greater than 1.2 overlying an electrode layer on thesubstrate and at least one of the plurality of chambers is configured tosubject the copper-indium composite material to a thermal process in asulfur-bearing environment to form a chalcogenide structure photovoltaicfilm.

In yet another embodiment, the present invention provides a method formanufacture of thin film photovoltaic modules in a system withmulti-chamber configuration. The method includes providing a substrateinto a first chamber of the system with multi-chamber configuration. Thesubstrate is optically transparent and has a lateral dimension of 1.5meter and greater. Additionally, the method includes forming anelectrode layer overlying the substrate in the first chamber andtransferring the substrate out of the first chamber for patterning theelectrode layer. The method further includes transferring the substratewith the patterned electrode layer in a second chamber of the systemwith multi-chamber configuration to form a copper (Cu)-bearing materiallayer overlying the electrode layer. Furthermore, the method includestransferring the substrate to a third chamber of the system withmulti-chamber configuration to form an indium (In) layer overlying thecopper-bearing material layer, which correspondingly leads to aformation of a Cu—In composite film with Cu-rich stoichiometry in termsof a Cu:In atomic ratio of 1.2:1 and greater. Moreover, the methodincludes subjecting the Cu—In composite film to a thermal treatmentprocess in a fourth chamber of the system with multi-chamberconfiguration. The fourth chamber comprises an environment includingsulfur-bearing species where the Cu—In composite film is transformedinto a copper-indium-disulfide material. The method also includesforming a photovoltaic absorber layer for a thin film photovoltaicmodule using the copper-indium-disulfide material.

Various additional objects, features and advantages of the presentinvention can be more fully appreciated with reference to the detaileddescription and accompanying drawings that follow.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a simplified view diagram of a system for large scalemanufacture of thin film photovoltaic devices according to an embodimentof the present invention;

FIG. 1B is a simplified view diagram of a system for large scalemanufacture of thin film photovoltaic devices according to analternative embodiment of the present invention;

FIG. 2 is a simplified view diagram of a control system for the systemfor large scale manufacture of thin film photovoltaic devices of FIG. 1according to an embodiment of the present invention;

FIG. 3 is a simplified view diagram of a single physical vapordeposition tool which can be part of a system for large scalemanufacture of thin film photovoltaic devices according to anotherembodiment of the present invention;

FIG. 4 is a simplified flow chart illustrating a method for large scalemanufacture of thin film photovoltaic devices according to an embodimentof the present invention;

FIG. 5 is a simplified flow chart illustrating a method for large scalemanufacture of thin film photovoltaic devices according to anotherembodiment of the present invention;

FIGS. 6-8 are simplified flow charts illustrating a method for largescale manufacture of thin film photovoltaic devices according to anotherembodiment of the present invention;

FIG. 9 is a simplified flow chart illustrating a method for large scalemanufacture of thin film photovoltaic devices according to anotherembodiment of the present invention;

FIG. 10 is a simplified flow chart illustrating a method for large scalemanufacture of thin film photovoltaic devices according to anotherembodiment of the present invention;

FIG. 11 is a simplified flow chart illustrating a method for large scalemanufacture of thin film photovoltaic devices according to an embodimentof the present invention;

FIG. 12 is a simplified flow chart illustrating a method for large scalemanufacture of thin film photovoltaic devices according to anotherembodiment of the present invention;

FIG. 13 is a simplified schematic diagram showing a system withmulti-chamber configuration for large scale manufacture of thin filmphotovoltaic modules according to an embodiment of the presentinvention;

FIGS. 14-16 are simplified schematic diagrams showing additionalprocesses of a method for large scale manufacture of thin filmphotovoltaic modules using multi-chamber configuration according to anembodiment of the present invention.

DETAILED DESCRIPTION

The present invention relates generally to photovoltaic materials. Moreparticularly, the present invention provides a method and system forlarge scale manufacture of multi junction and single junction solarmodules using integrated manufacturing systems for thin and thick filmphotovoltaic materials. Merely by way of example, the present method andstructure have been implemented using a solar module having multiplethin film materials, but it would be recognized that the invention mayhave other configurations.

FIG. 1A is a simplified view diagram of a system 100 for large scalemanufacture of thin film photovoltaic devices according to an embodimentof the present invention. This diagram is merely an example, whichshould not unduly limit the scope of the claims herein. One of ordinaryskill in the art would recognize other variations, modifications, andalternatives. As shown, system 100 includes load locks #1 and #2 forproviding an interface between system 100 and the environment. System100 also includes process stations P1, P2, . . . , Pm, and transportstations T1, T2, T3, . . . , Tn. Each process station is configured toperform a process required to form the thin film photovoltaic device.Depending on the embodiment, the processes can include thin filmformation, patterning, etching, annealing, etc. The process stations arecapable of supplying process gases, maintaining process temperature,maintaining process pressure, etc.

In a specific embodiment, a substrate, e.g. a glass substrate, isentered into system 100 through lord lock #1, which can be pumped downto a reduced pressure. Transport stations T1-Tn are configured to allowthe substrate to be transported between a load lock and a processstation, or between two process stations. The transport stations canprovide a controlled ambient to maintain cleanliness of the substrate.For example, a transport station can allow a substrate to be transferredin a vacuum. In another example, a transport station may provide aninert gas ambient of, e.g. nitrogen or argon, and can be maintained atatmospheric pressure or at a reduced pressure.

FIG. 1B is a simplified view diagram of a system 150 for large scalemanufacture of thin film photovoltaic devices according to analternative embodiment of the present invention.

This diagram is merely an example, which should not unduly limit thescope of the claims herein. One of ordinary skill in the art wouldrecognize other variations, modifications, and alternatives. As shown,system 150 includes a load lock, multiple process stations, and multipletransport stations. The functions of the load lock, process stations,and transport stations are similar to those discussed above inconnection with system 100 in FIG. 1. System 150, however, has adifferent configuration. A central load lock is connected to transportstations T1, T2, . . . , Tn, which in turn are coupled to processstations P1, P2, . . . , Pn. In a specific embodiment, after eachprocess steps, the substrate is returned to the central load lock, andthe next process station is selected for the next process. Of course,one of ordinary skilled in the art can recognize other configurations,variations, modifications.

System 100 and system 150 are examples of systems for large scalemanufacture of thin film photovoltaic devices according to embodimentsof the present invention. Depending on the embodiment, the system isconfigured to allow formation of junction between the window layer andthe absorber layer without breaking vacuum and to keep moisture,particles, and oxygen from contaminating the substrate and the deviceduring process. In a specific example, load locks and transport stationsare provided. Inert gases can also be used at reduced or atmosphericpressure.

In a specific embodiment, a process sequence in system 100 for largescale manufacture of photovoltaic devices can be briefly summarizedbelow.

-   -   1. Load substrate into the load-lock;    -   2. Pump down the load lock, turn on the heater, and flow inert        gas (Ar or N₂) until substrate reaches set temperature;    -   3. Transfer substrate into the selected process station chamber;    -   4. Flow process gas, turn on sputtering power, and start the        sputtering process;    -   5. Once process is finished, select the next station (process or        transfer station), transfer the substrate;    -   6. Perform the next process in the next process station; and    -   7. After the process is completed, the substrate is transferred        to the second load-lock.

The second load lock is vented, and the substrate is removed from thesystem.

FIG. 2 is a simplified view diagram of a control system 200 for thesystem for large scale manufacture of thin film photovoltaic devices ofFIG. 1 according to an embodiment of the present invention. This diagramis merely an example, which should not unduly limit the scope of theclaims herein. One of ordinary skill in the art would recognize othervariations, modifications, and alternatives. As shown, control system200 includes processors, memories, user interface devices, and interfaceto network. In an embodiment, the control system performs variouscontrol functions of, for example, system 100 or system 150.

In a specific embodiment, the control system 200 also controls variousdiagnostic tools disposed in-situ in systems 100 and 150 for criticalprocess steps, such as formation of absorber layer and the window layer.Thin film properties are monitored in-situ. Electrical and opticalproperties are also measured in-situ in the process station. Theelectrical properties are measured either using probes or using acontactless method. The electrical properties are also used to detectshunts in the thin films. The data is used in feedback to adjust secondprocess for absorber layer or window layer. Alternatively, thediagnostic and monitoring tools can also be used in a feed forwardprocess for adjusting the next process for a second cell or within thecell design. In an embodiment, a process can be stopped based on in-situmeasurement data. In another embodiment, process parameters are adjustedbefore the process is resumed.

FIG. 3 is a simplified view diagram of a single physical vapordeposition (PVD) tool which can be part of a system for large scalemanufacture of thin film photovoltaic devices according to anotherembodiment of the present invention. This diagram is merely an example,which should not unduly limit the scope of the claims herein. One ofordinary skill in the art would recognize other variations,modifications, and alternatives. A PVD process is often carried out bysputtering in which collision of high-energy particles with sputteringtargets to deposit materials ejected from the sputtering targets on asubstrate. In a sputtering process thin films can be formed to a uniformthickness over a large area, and the composition ratio of thin films canbe easily adjusted. In magnetron sputtering a magnetic field is used tohelp create a high-density plasma of energetic particles in a reactionchamber, usually under a low pressure.

As shown in FIG. 3, a substrate 31 is disposed in a vacuum chamber 32. Atarget 34 is disposed on the opposite side from the substrate 32.Magnets 35 are disposed behind the target 34 to form magnetic fieldlines of predetermined directions. In addition, a power supply unit 37supplies a voltage to an electrode 38 which is coupled to target 34.During processing, a vacuum is maintained in the chamber, a gas such asargon is introduced in the chamber, and electric discharge createsplasma. Energetic particles collide with the target and cause atoms tobe ejected from the target and deposited on the substrate to form a thinfilm.

One or more process stations in system 100 in FIG. 1A or system 150 inFIG. 1B may include a balanced magnetron sputtering station. In aspecific embodiment, the magnet field are arranged to focus the plasmafor large areas of substrate and to provide a uniform thin film over alarge area. Depending on the embodiment, the size of the substrate canbe 2′ by 5′ or larger. In an embodiment, when the sputtering targets canbe about five foot wide or even wider, scanning magnetrons is used tokeep uniformity of films. In an embodiment, the sputtering stationsallow formation of thin films over large areas substantially free ofpin-holes.

According to embodiments of the present invention, various methods areprovided for large scale manufacture of photovoltaic devices. Examplesof these methods are discussed below in connection with the drawingsprovided in FIGS. 4-12. It is noted that, in the examples discussedbelow, transferring the substrate in a controlled ambient can be carriedout in different way. For example, the substrate can be transferredunder reduced pressure, or the substrate can be transferred in anambient of an inert gas, such as N₂ and Ar. Alternatively, the transfercan be carried out under atmospheric pressure in an inert gas.Additionally, physical deposition processes are used extensively in theexamples discussed below. It is noted that in a specific embodiment, thephysical deposition processes include sputtering using balancedmagnetron.

In various embodiments discussed below, the substrate is asemiconductor, for example, silicon, germanium, compound semiconductormaterial such as a III-V gallium arsenide, germanium, silicon germanium,and others. Alternatively, the substrate can be a transparent substratesuch as glass, quartz, fused silica, and others. Other examples of thesubstrate include a polymer material or a metal material. The metalchalcogenide material in the examples discussed below include copper(II) oxide (CuO) having a bandgap of about 1.2 eV and others. In aspecific embodiment, the first bandgap is less than the second bandgap.

The conductor layers used in various embodiments can be aluminum,tungsten, or other metallic material. The conductor layer can also be atransparent conducting oxide material such as ZnO:Al, SnO:F, ITO, orothers. The conductor layer can also be a conductive polymer material.Examples of various materials used in photovoltaic devices can be foundin U.S. patent application Ser. No. 11/748,444, filed May 14, 2007, U.S.patent application Ser. No. 11/804,019, filed May 15, 2007, andconcurrently filed U.S. Provisional Patent Application No. 60/988,099,filed Nov. 14, 2007. All these applications are commonly assigned, andtheir contents are hereby incorporated by reference for all purposes.

FIG. 4 is a simplified flow chart illustrating a method for large scalemanufacture of single junction thin film photovoltaic devices accordingto an embodiment of the present invention. This diagram is merely anexample, which should not unduly limit the scope of the claims herein.One of ordinary skill in the art would recognize other variations,modifications, and alternatives. As shown, the method of manufacturing asingle junction photovoltaic device, also known as the substrate method,can be summarized as follows.

-   -   1. loading a substrate into a load lock station, the substrate        including a surface region;    -   2. transferring the substrate under a controlled ambient to a        first process station;    -   3. using a first physical deposition process in the first        process station to cause formation of a first conductor layer        overlying the surface region of the substrate;    -   4. transferring the substrate under reduced pressure to a second        process station;    -   5. using a second physical deposition process in the second        process station to cause formation of a first p-type absorber        material, the first p-type absorber material comprising at least        a first metal chalcogenide material overlying the first        conductor layer, the first p-type absorber material being        characterized by a first bandgap range and a first thickness        range;    -   6. monitoring properties of the first p-type absorber material        in the second process station;    -   7. transferring the substrate in a controlled ambient to a third        process station;    -   8. using a third physical deposition process in the third        process station to cause formation of a first n-type window        layer, the first n-type window layer comprising at least a        second metal chalcogenide material overlying the first p-type        absorber layer; in a specific embodiment, the third physical        deposition process being determined based on the properties of        the first p-type absorber material;    -   9. transferring the substrate under a controlled ambient to a        fourth process station; and    -   10. using a fourth physical deposition process in the fourth        process station to cause formation of a second conductor layer        overlying the second buffer layer.

In a specific embodiment, the method also includes forming a secondbarrier layer overlying the first conductor layer. In anotherembodiment, the method includes forming a first high resistivity layeroverlying the first conductor layer before the formation of the firstp-type absorber material, the first buffer layer being characterized bya resistivity greater than about 10 kohm-cm. The buffer layer issometimes referred to as a high-resistance transparent conducting oxidebuffer layers or HRT. The HRT can minimize effect of shunt defects. In aspecific embodiment, the resistivity HRT is about 10 k ohm percentimeter, whereas the resistivity of the transparent conduction oxidelayer (TCO) is about 7 to 10 ohms per centimeter. In another specificembodiment, the method further includes in-situ monitoring properties ofthe layer being formed in each process station and determining a processcondition in a subsequent physical deposition process based on dataobtained in the monitoring of the earlier processes.

FIG. 5 is a simplified flow chart illustrating a method for large scalemanufacture of thin film photovoltaic devices according to anotherembodiment of the present invention. This diagram is merely an example,which should not unduly limit the scope of the claims herein. One ofordinary skill in the art would recognize other variations,modifications, and alternatives. As shown, another method ofmanufacturing a single junction photovoltaic device, also known as thesuperstrate method, can be briefly summarized below.

-   -   1. loading a substrate into a load lock station, the substrate        including a surface region;    -   2. transferring the substrate under a controlled ambient to a        first process station;    -   3. using a first physical deposition process in the first        process station to cause formation of a first conductor layer        overlying the surface region of the substrate;    -   4. transferring the substrate under reduced pressure to a second        process station;    -   5. using a second physical deposition process in the second        process station to cause formation of a first n-type window        layer, the first n-type window layer comprising at least a        second metal chalcogenide material overlying the first p-type        absorber layer;    -   6. monitoring properties of the first p-type absorber material        in the second process station;    -   7. transferring the substrate in a controlled ambient to a third        process station;    -   8. using a third physical deposition process in the third        process station to cause formation of a first p-type absorber        material, the first p-type absorber material comprising at least        a first metal chalcogenide material overlying the first        conductor layer, the first p-type absorber material being        characterized by a first bandgap range and a first thickness        range; in a specific embodiment, the third physical deposition        process is determined based on the properties of the first        n-window layer;    -   9. transferring the substrate under a controlled ambient to a        fourth process station; and    -   10. using a fourth physical deposition process in the fourth        process station to cause formation of a second conductor layer        overlying the second buffer layer.

In a specific embodiment, the method of FIG. 5 also includes a feedforward control. The method includes the additional processes of in-situmonitoring properties of the layer being formed in each process station,and determining a process condition in a subsequent physical depositionprocess based on data obtained in the monitoring of the earlierprocesses.

FIGS. 6-8 are simplified flow charts illustrating a method for largescale manufacture of thin film photovoltaic devices according to anotherembodiment of the present invention. This diagram is merely an example,which should not unduly limit the scope of the claims herein. One ofordinary skill in the art would recognize other variations,modifications, and alternatives. As shown, the method is for making twophotovoltaic devices stacked to make a tandem device, with eachphotovoltaic device having two terminals. The method can be brieflysummarized as follows.

-   -   1. forming a top photovoltaic device using the superstate method        of FIG. 5 as described above;    -   2. forming a bottom photovoltaic device using the substrate        method of FIG. 4 as described above;    -   3. forming an insulator layer overlying the bottom photovoltaic        device; and    -   4. mounting the top photovoltaic device over the insulator layer        and the bottom photovoltaic device.

In a specific embodiment, the top device, the insulator layer, and thebottom layer are laminated together with an EVA material. Of course,other kinds of adhesive materials can also be used. In another specificembodiment, the method further includes a feed forward process whichallows monitoring device properties of the top photovoltaic device andadjusting device parameters and process conditions for the bottomphotovoltaic device.

FIG. 9 is a simplified flow chart illustrating a method for large scalemanufacture of thin film photovoltaic devices according to anotherembodiment of the present invention. This diagram is merely an example,which should not unduly limit the scope of the claims herein. One ofordinary skill in the art would recognize other variations,modifications, and alternatives. As shown, the method is formanufacturing a tandem photovoltaic device, which includes twophotovoltaic junctions but has only two external terminals. The methodcan be briefly summarized as follows.

-   -   1. loading a substrate into a load lock station, the substrate        including a surface region;    -   2. transferring the substrate in a controlled ambient to a first        process station;    -   3. using a first physical deposition process in the first        process station to cause formation of a first conductor layer        overlying the surface region of the substrate;    -   4. transferring the substrate in a controlled ambient to a        second process station;    -   5. using a second physical deposition process in the second        process station to cause formation of a first p-type absorber        material, the first p-type absorber material comprising at least        a first metal chalcogenide material overlying the first        conductor layer, the first p-type absorber material being        characterized by a first bandgap range and a first thickness        range;    -   6. transferring the substrate in a controlled ambient to a third        process station;    -   7. using a third physical deposition process in the third        process station to cause formation of a first n-type window        layer, the first n-type window layer comprising at least a        second metal chalcogenide material overlying the first p-type        absorber layer;    -   8. transferring the substrate in a controlled ambient to a        fourth process station;    -   9. using a fourth physical deposition process in the fourth        process station to cause formation of an n++ type semiconductor        material;    -   10. transferring the substrate in a controlled ambient to a        fifth process station;    -   11. using a fifth physical deposition process in the fifth        process station to cause formation of an p++ type semiconductor        material, the p++ semiconductor material and the n++        semiconductor material forming a tunneling junction layer;    -   12. transferring the substrate in a controlled ambient to a        sixth process station;    -   13. using a sixth physical deposition process in the sixth        process station to cause formation of a second p-type absorber        material, the second p-type absorber material comprising at        least a third metal chalcogenide material overlying the        tunneling junction layer, the second p-type absorber material        being characterized by a second bandgap range and a second        thickness range;    -   14. transferring the substrate in a controlled ambient to a        seventh process station;    -   15. using a seventh physical deposition process in the seventh        process station to cause formation of a second n-type window        layer, the second n-type window layer comprising at least a        fourth metal chalcogenide material overlying the second absorber        layer;    -   16. transferring the substrate in a controlled ambient to an        eighth process station; and    -   17. using an eighth physical deposition process in the eighth        process station to cause formation of a second conductor layer.

In a specific embodiment of the method of FIG. 9, the method alsoincludes feed forward control, for example, in-situ monitoringproperties of the layer being formed in each process station anddetermining a process condition in a subsequent physical depositionprocess based on data obtained in the monitoring of the earlierprocesses. In a specific embodiment, the method also includes forming afirst buffer layer overlying the first conductor layer before theformation of the first p-type absorber material. The first buffer layerhas a resistivity greater than about 10 kohm-cm. In another embodiment,a second 1 buffer layer is formed overlying the second n-type windowlayer before the formation of the second conductor layer. The secondbuffer layer is characterized by a resistivity greater than about 10kohm-cm.

FIG. 10 is a simplified flow chart illustrating a method for large scalemanufacture of thin film photovoltaic devices according to anotherembodiment of the present invention. This diagram is merely an example,which should not unduly limit the scope of the claims herein. One ofordinary skill in the art would recognize other variations,modifications, and alternatives. As shown, FIG. 10 illustrates a methodfor manufacturing a tandem cell having three external terminals. Inother words, the top and bottom photovoltaic devices share a commonconductor which is coupled to an external terminal. The method can bebriefly summarized below.

-   -   1. loading a substrate into a load lock station, the substrate        including a surface region;    -   2. transferring the substrate in a controlled ambient to a first        process station;    -   3. using a first physical deposition process in the first        process station to cause formation of a first conductor layer        overlying the surface region of the substrate;    -   4. transferring the substrate in a controlled ambient to a        second process station;    -   5. using a second physical deposition process in the second        process station to cause formation of a first p-type absorber        material, the first p-type absorber material comprising at least        a first metal chalcogenide material overlying the first        conductor layer, the first p-type absorber material being        characterized by a first bandgap range and a first thickness        range;    -   6. transferring the substrate in a controlled ambient to a third        process station;    -   7. using a third physical deposition process in the third        process station to cause formation of a first n-type window        layer, the first n-type window layer comprising at least a        second metal chalcogenide material overlying the first p-type        absorber layer;    -   8. transferring the substrate in a controlled ambient to a        fourth process station;    -   9. optionally, using a fourth physical deposition process in the        fourth process station to cause formation of a high resistive        layer;    -   10. transferring the substrate in a controlled ambient to a        fifth process station;    -   11. using a fifth physical deposition process in the fifth        process station to cause formation of a second conductive layer;    -   12. transferring the substrate in a controlled ambient to a        sixth process station;    -   13. using a sixth physical deposition process in the sixth        process station to cause formation of a second p-type absorber        material, the second p-type absorber material comprising at        least a third metal chalcogenide material overlying the        tunneling junction layer, the second p-type absorber material        being characterized by a second bandgap range and a second        thickness range;    -   14. transferring the substrate in a controlled ambient to a        seventh process station;    -   15. using a seventh physical deposition process in the seventh        process station to cause formation of a second n-type window        layer, the second n-type window layer comprising at least a        fourth metal chalcogenide material overlying the second absorber        layer;    -   16. transferring the substrate in a controlled ambient to an        eighth process station; and    -   17. using an eighth physical deposition process in the eighth        process station to cause formation of a third conductor layer.

In a specific embodiment, the method of FIG. 10 also includes feedforward control. That is, the method also includes in-situ monitoringproperties of the layer being formed in each process station anddetermining a process condition in a subsequent physical depositionprocess based on data obtained in the monitoring of the earlierprocesses.

FIG. 11 is a simplified flow chart illustrating a method for large scalemanufacture of thin film photovoltaic devices according to an embodimentof the present invention. This diagram is merely an example, whichshould not unduly limit the scope of the claims herein. One of ordinaryskill in the art would recognize other variations, modifications, andalternatives. As shown, FIG. 11 illustrates a method for large scalemanufacturing of single junction photovoltaic devices including feedforward control. The method can be summarized briefly as follows.

-   -   1. loading a substrate into a load lock station, the substrate        including a surface region;    -   2. transferring the substrate under a controlled ambient to a        first process station;    -   3. using a first physical deposition process in the first        process station to cause formation of a first conductor layer        overlying the surface region of the substrate;    -   4. transferring the substrate under a controlled ambient to a        second process station;    -   5. using a second physical deposition process in the second        process station to cause formation of a first p-type absorber        material, the first p-type absorber material comprising at least        a first metal chalcogenide material overlying the first        conductor layer, the first p-type absorber material being        characterized by a first bandgap range and a first thickness        range;    -   6. monitoring properties of the first p-type absorber material        in the second process station;    -   7. determining a process condition in a third physical        deposition process based on data obtained in the monitoring;    -   8. transferring the substrate in a controlled ambient to a third        process station;    -   9. using the third physical deposition process in the third        process station to cause formation of a first n-type window        layer, the first n-type window layer comprising at least a        second metal chalcogenide material overlying the first p-type        absorber layer,    -   10. transferring the substrate under a controlled ambient to a        fourth process station; and    -   11. using a fourth physical deposition process in the fourth        process station to cause formation of a second conductor layer        overlying the second buffer layer.

FIG. 12 is a simplified flow chart illustrating a method for large scalemanufacture of thin film photovoltaic devices according to anotherembodiment of the present invention. This diagram is merely an example,which should not unduly limit the scope of the claims herein. One ofordinary skill in the art would recognize other variations,modifications, and alternatives. As shown, FIG. 12 illustrates a methodfor making a tandem photovoltaic device having a bottom photovoltaiccell and a top photovoltaic cell using methods similar to those of FIGS.4-11, but also includes in-situ monitoring of the properties of thelower cell. These properties include thin film material properties andelectrical and optical properties of the junction. If the properties arenot within a predetermined specification, then the process and deviceparameters of the upper cell are adjusted. Subsequently the adjustedprocess is used to make the upper cell.

According to another specific embodiment of the present invention, amethod is provided for making a single junction photovoltaic deviceincluding feed forward control. The method can be briefly summarizedbelow.

-   -   1. loading a substrate into a load lock station, the substrate        including a surface region;    -   2. transferring the substrate under a controlled ambient to a        first process station;    -   3. using a first physical deposition process in the first        process station to cause formation of a first conductor layer        overlying the surface region of the substrate;    -   4. transferring the substrate under a controlled ambient to a        second process station;    -   5. using a second physical deposition process in the second        process station to cause formation of a first p-type absorber        material, the first p-type absorber material comprising at least        a first metal chalcogenide material overlying the first        conductor layer, the first p-type absorber material being        characterized by a first bandgap range and a first thickness        range;    -   6. monitoring properties of the first p-type absorber material        in the second process station;    -   7. determining a process condition in a third physical        deposition process based on data obtained in the monitoring;    -   8. transferring the substrate in a controlled ambient to a third        process station;    -   9. using the third physical deposition process in the third        process station to cause formation of a first n-type window        layer, the first n-type window layer comprising at least a        second metal chalcogenide material overlying the first p-type        absorber layer,    -   10. transferring the substrate under a controlled ambient to a        fourth process station; and    -   11. using a fourth physical deposition process in the fourth        process station to cause formation of a second conductor layer        overlying the second buffer layer.

FIG. 13 is a simplified schematic diagram showing a system withmulti-chamber configuration for large scale manufacture of thin filmphotovoltaic module according to an embodiment of the present invention.This diagram is merely an example, which should not unduly limit thescope of the claims herein. One of ordinary skill in the art wouldrecognize other variations, modifications, and alternatives. As shown, asystem 1300 (at least partially) with multi-chamber configuration forlarge scale manufacture of thin film photovoltaic modules is providedand several thin film processes are illustrated. In particular, a largesubstrate 1310 is provided as shown as a first step I into a Chamber 1of the system 1300 with multi-chamber configuration. In an embodiment, atransfer tool 1390 including a process stage is used to support thelarge substrate 1310. Additionally, one or more loading locks orintermediate chambers 1306 can be used to assist the execution of in/outsubstrate transfer process. FIG. 13 merely shows a schematic example ofthe transfer tool 1390 and merely shows a location of the load lockchamber 1306 without providing structure details and even not shown intrue dimensions. In an embodiment, the substrate 1310 is an opticallytransparent solid material. For example, the substrate 1310 can be aglass (e.g., the popular soda lime window glass), quartz, fused silica,or a plastic, or other optically transparent composite materials. In anexample, the large substrate 1310 can be as large as 1.5 meters orgreater in lateral dimension that is used for direct manufacture thinfilm photovoltaic module thereon. Depending upon embodiments, thesubstrate 1310 can be a single material, multiple materials, which arelayered, composites, or stacked, including combinations of these, andthe like. Of course there can be other variations, modifications, andalternatives.

As shown in FIG. 13 the substrate 1310 includes a surface region 1311and is held in the process stage exposing to a deposition sourcedisposed in Chamber 1. For example, the deposition source can be asputtering target 1301 held a short distance above the surface region1311. In an embodiment, the Chamber 1 is used for forming an electrodelayer of a thin film photovoltaic module. In particular, an electrodelayer 1320 can be sputtering deposited overlying the surface region 1311of the substrate 1310. For example, the sputtering target 1301 made ofsubstantially conductive material is predisposed. The conductivematerial for the electrode layer includes molybdenum, tungsten,aluminum, copper, silver, and the other metals. In an implementation,three sputtering targets made of 99.9999% pure molybdenum (Mo) materialare used. The first target is used for forming a first Mo sublayer ofthe electrode layer 1320 and the other two target sequentially disposedin Chamber 1 are used for forming a second Mo sublayer of the electrodelayer 1320.

The Chamber 1 can be maintained in a vacuum condition measured with apressure of about 10 microbar. One or more working gases for assistingthe sputtering process can be flowed in with rate control. For example,during the formation of the first Mo sublayer one working gas is pureArgon gas with a flow rate of about 100 sccm and another is Argon gasmixed with about 1% Oxygen gas with a flow rate of about 5-10 sccm. Thefirst Mo sublayer can be 50 to 400 Angstroms according to embodiments ofthe invention. Subsequently, the second Mo sublayer can be formedoverlying the first Mo sublayer. In an embodiment, two sputteringtargets made of molybdenum material are disposed in series to form thesecond Mo sublayer with a total thickness of 3000 to 3500 Angstroms.Using two targets may allow the sputtering process to occur at arelative lower power density. In another embodiment, a single molybdenumtarget is also capable of forming the total thickness of the second Mosublayer. During the formation of the second Mo sublayer, a pure Argongas with a flow rate of about 100 sccm is introduced into the Chamber 1.

Of course, other thin film deposition techniques may be used includingevaporation (e.g., using electron beam), chemical vapor deposition,electro-plating, atomic layer deposition, or any combination of these,and the like according to a specific embodiment. The electrode layerwith a total thickness of about 300 to 400 nm can be characterized byresistivity of about 100 ohm-cm to 10 ohm-cm and less according to aspecific embodiment. As shown in FIG. 13, the formation of the electrodelayer 1320 refers a completion of a second step II performed in theChamber 1.

Referring to FIG. 13, after the process finishes in the Chamber 1, thesubstrate 1310 with overlying electrode layer 1320 can be transferredout of the Chamber 1 by the transfer tool 1390 via a load lock 1306. Inan embodiment, the process of manufacture thin film photovoltaic moduleincludes patterning the electrode layer. The electrode layer 1320 needsto be reconfigured and patterned to form a plurality of electrodes thatcan be used to draw photo-electric currents when the thin filmphotovoltaic module finally is set to use under the sun. In particular,the patterning process can use a mechanical patterning technique, alaser patterning technique, a chemical patterning technique, etc. In animplementation, the patterning process is performed in atmosphereenvironment outside the Chamber 1. The transfer tool 1390 is configuredto move the substrate from the Chamber 1 through one of loading lock1306 to a specific work station for performing the patterning process.

The lower left part of FIG. 13 schematically shows that a patterningprocess is performed, as a step III, to the electrode layer 1320 to formone or more electrode pattern 1321. In an embodiment, laser ablation isused for forming the electrode pattern 1321. The electrode layer 1320 issubjected to a laser radiation at certain predetermined locations. Thelaser radiation can be a laser beam from a pulsed laser source or CWlaser source. The laser beam can be aligned from above the electrodelayer 1320 or from a backside of the transparent substrate 1310. Forexample the laser beam is generated from a Nd:YAG infrared Q-Switchedpulse laser source with wavelength of about 1065 nm. As the laser beamirradiates the electrode layer 1320, an ablation process occurs duringwhich a portion of the electrode layer 1320 under the laser beam can beremoved from the substrate 1310. In particular, the laser energy causesvaporization of electrode layer material, e.g., molybdenum, under a beamspot or simply blows away from the substrate 1310. The laser beam can bescanned along a predetermined pattern and subsequently additional amountof certain conducting material is removed. Each time after the laserbeam ablates a spot of electrode layer material, the beam is moved (maybe pulsed OFF) to a next spot, then the laser power is pulsed ON toirradiate the new spot again to cause the electrode layer material underthe new spot to be removed. As a result, one or more electrode patterns1321 form in the electrode layer 1320.

Next, the substrate with patterned electrode layer can be furthertransferred into the system with multi-chamber configuration. Inparticular as shown in FIG. 13, the substrate 1310 is provided into aChamber 2 of the system 1300. The Chamber 2 is a process chamberdesigned to couple with a load lock 1306 which may also coupled to theChamber 1. In certain implementation, the patterning process can bedirectly performed within the Chamber 1 so that the transfer tool 1390can further load the substrate 1310 directly from the Chamber 1 via theload lock 1306 into the Chamber 2 for continuing the large scalemanufacture of the thin film photovoltaic module. Of course, there canbe many alternatives, variations, and modifications.

In an embodiment, Chamber 2 is configured to form a copper layeroverlying the electrode layer formed in last process. In particular, acopper (Cu)-bearing layer 1330 can be formed overlying the electrodelayer 1320 using another sputtering process. In an example, thesubstrate 1310 with overlying electrode layer 1320 is exposed to aCu-bearing sputtering target 1302 in Chamber 2. Please note, theelectrode layer 1320 on the substrate 1310 likely is a layer with one ormore electrode patterns 1321 formed in a previous step, even though nospecific pattern is explicitly shown in the schematic illustrating ofthe process within the Chamber 2. In another example, a DC magnetronsputtering technique can be used to deposit the Cu-bearing layer 1330onto the electrode layer 1320 under a following condition: Thedeposition is controlled to be about a vacuum environment having apressure of 6.2 mTorr or lower with Ar gas. The gas flow rate is set toabout 32 sccm. The deposition temperature can be just at roomtemperature without need of intentionally heating the substrate. Ofcourse, minor heating may be resulted due to the plasma generated duringthe deposition. Additionally, the DC power supply of about 115 W may berequired. According to certain embodiments, DC power in a range from 100W to 150 W is suitable depending specific cases with differentmaterials. The full deposition time for the Cu-bearing layer 1330 ofabout 330 nm thickness is about 6 minutes or more. Of course, thedeposition condition can be varied and modified according to a specificembodiment. For example, a Cu-bearing target also includes a gallium(Ga) content or both Cu target and Ga target are disposed in series inthe Chamber 2 so that the Cu-bearing layer 1330 comprises Cu—Ga alloy.

Referring to FIG. 13 again, after the formation of the Cu-bearing layer1330, the system 1300 is configured to transfer the substrate 1310 withoverlying electrode layer 1320 and Cu-bearing layer 1330 from theChamber 2 to a next chamber, Chamber 3. In an embodiment, this chamberis designed to allow the transfer tool 1390 further load the substratein and perform one or more processes of providing an indium (In) layeroverlying the Cu-bearing layer for manufacture a thin film photovoltaicmodule. In particular as shown, the indium In layer 1340 is formedoverlying the copper Cu-bearing layer 1330. In an implement, the indiumlayer can be deposited using a sputtering process and the Cu-bearinglayer 1330 is exposed to an In-based sputtering target 1303 when thesubstrate 1310 with overlying electrode layer 1320 and Cu-bearing layer1330 is loaded into the Chamber 3. In an example, the indium sputteringtarget contains 99.999% pure indium material and a DC magnetronsputtering technique can be used to deposit the In layer 1340 overlyingthe Cu layer 120 under a similar condition for depositing the Cu-bearinglayer 1330. The deposition time for the indium layer 1340 may be shorterthan that for Cu-bearing layer 1330. For example, 2 minutes and 45seconds may be enough for depositing an In layer of about 410 nm inthickness according to a specific embodiment. In another example, theindium layer 1340 is provided overlying the Cu-bearing layer 1330 by anelectro-plating process, or other techniques dependent on specificembodiment.

According to embodiments of the present invention, FIG. 13 illustrates amethod and system with multi-chamber configuration of forming amultilayered structure comprising at least copper and indium material ona transparent substrate for manufacture of a thin film photovoltaicmodule. In an embodiment, the Cu-bearing layer 1330 as well as theindium layer 1340 are provided with a controlled stoichiometriccomposition so that the multilayered structure is a Cu-rich compositematerial with an atomic ratio of Cu:In greater than 1 therein. Forexample, the atomic ratio of Cu:In within the multilayered structure canbe in a range from 1.2:1 to 2.0:1 or larger depending upon the specificembodiment. In an implementation, the atomic ratio of Cu:In is between1.35:1 and 1.60:1. In another implementation, the atomic ratio of Cu:Inis selected to be about 1.55:1. In a specific embodiment, the formationprocess of indium layer 1340 substantially causes no change in atomicstoichiometry in the copper layer 1330 formed earlier. Alternatively,the formation process of the indium layer 1340 can be performed earlierwithin the Chamber 2 overlying the electrode layer 1320 while theformation process of the Cu-bearing layer 1330 is then performed laterwithin the Chamber 3 overlying the indium layer 1340.

Referring to FIG. 13 further, the system 1300 is configured to use themulti-chamber configuration for forming a thin film photovoltaic moduleaccording to an embodiment of the present invention. As shown, after theformation of a multilayered structure comprising at least an indiumlayer 1340 over a Cu-bearing layer 1330, the substrate 1310 bearing themultilayered structure is further transferred from the Chamber 3 to aChamber 4 by the transfer tool 1390 to subject a thermal treatmentprocess. As an embodiment, the Chamber 4 is configured to supply thermalenergy using a plurality of heaters 1305 and provide an environment 1307containing a sulfur bearing species 1308. The plurality of heaters 1305are capable of heat the Chamber 4 to a temperature of about 400 DegreesCelsius to about 600 Degrees Celsius for at least about three to fifteenminutes. In a specific embodiment, the plurality of heaters 1305combined with the Chamber 4 are configured to be a rapid thermalprocessor. In one example, the sulfur bearing species 1308 are in afluid phase. As an example, the sulfur can be provided in a solution,which has dissolved Na₂S, CS₂, (NH₄)₂S, thiosulfate, and others.

In a preferred embodiment, the sulfur bearing species 1308 are hydrogensulfide in gas phase flowed through a valve into the Chamber 4. In otherembodiments, the sulfur bearing species can be provided in a solid phaseand heated or allowed to boil, which vaporizes into a gas phase sulfur.In particular, the gas phase sulfur is reacting to the indium/copperlayers within the environment 1307 with a temperature about 500 DegreesCelsius. In other embodiments, other combinations of sulfur species canbe used. Of course, the thermal treatment process includes certainpredetermined ramp-up and ramp down period with certain predeterminedspeed for temperature changes. For example, the thermal treatmentprocess is a rapid thermal annealing process. The hydrogen sulfide gasis provided through one or more nozzles with a suitable flow ratecontrol. During the process Chamber 4 can be configured to control thehydrogen sulfide gas pressure using one or more pumps (not shown). Ofcourse, there can be other variations, modifications, and alternatives.

In an alternative embodiment, the sulfur species can be provided as alayer overlying the indium and copper-bearing layers or copper andindium layers. In a specific embodiment, the sulfur material is providedas a thin layer or patterned layer. Depending upon the embodiment, thesulfur species can be provided as a slurry, powder, solid material, gas,paste, or other suitable form. Of course, there can be other variations,modifications, and alternatives. Accordingly, the Chamber 4 of thesystem 1300 can be reconfigured to adapt those alternative sulfurincorporation processes.

Referring back to the FIG. 13, the thermal treatment process performedin the Chamber 4 causes a reaction between copper indium compositematerial within the multilayered structure formed on the substrate 1310and the gas phase sulfur bearing species 1308 introduced in the Chamber4. As a result of the reaction, a layer of copper indium disulfidematerial 1360 (or a copper indium disulfide thin film) can be formed. Inone example, the copper indium disulfide material 1360 is transformedfrom the copper indium composite material by incorporating sulfurions/atoms stripped or decomposed from the sulfur bearing species 1308into the indium layer 1340 overlying the Cu-bearing layer 1330 withindium atoms and copper atoms mutually diffusing therein. In anembodiment, the thermal treatment process would result in a formation ofa cap layer 1370 over the transformed copper indium disulfide material1360. The cap layer 1370 contains substantially copper sulfide materialbut substantially free of indium atoms. The cap layer 1370 issubstantially thinner than the copper indium disulfide material 1360.Depending on the applications, the thickness of the copper sulfidematerial 1370 is on an order of about five to ten nanometers and greaterassociated with original Cu—In composite material made of an indiumlayer 1340 overlying the Cu-bearing layer 1330. The cap layer 1370includes a surface region 1371 of the same copper sulfide materialsubstantially free of indium atoms. In a specific embodiment, theformation of this cap layer 1370 is under a Cu-rich stoichiometryconditions within the original Cu—In composite material. Of course,there can be other variations, modifications, and alternatives.

FIGS. 14-16 are simplified schematic diagrams illustrating additionalprocesses using the system with multi-chamber configuration formanufacture of a thin film photovoltaic module according to anembodiment of the present invention. These diagrams are merely examples,which should not unduly limit the claims herein. One skilled in the artwould recognize other variations, modifications, and alternatives. Asshown in FIG. 14, a dip process 1400 is performed to the copper sulfidematerial 1370 that covers the copper indium disulfide thin film 1360. Inparticular, the dip process is an etching process performed by exposingthe surface region 1371 of the copper sulfide material 1370 to 1 toabout 10 wt % solution of potassium cyanide 1410 according to a specificembodiment. The potassium cyanide in solution 1410 acts as an etchantcapable of selectively removing copper sulfide material 1370. Theetching process starts from the exposed surface region 1371 down to thethickness of the copper sulfide material 1370 and substantially stops atthe interface between the copper sulfide material 1370 and copper indiumdisulfide material 1360. As a result the copper sulfide cap layer 1370can be selectively removed by the etching process so that a new surfaceregion 1368 of the remaining copper indium disulfide thin film 1360 isexposed according to a specific embodiment. In a preferred embodiment,the etch selectivity is about 1:100 or more between copper sulfidematerial and copper indium disulfide thin film. In other embodiments,other selective etching species can be used. In a specific embodiment,the etching species can be hydrogen peroxide. In other embodiments,other techniques including electro-chemical etching, plasma etching,sputter-etching, or any combination of these can be used. In a specificembodiment, the copper sulfide material can be mechanically removed,chemically removed, electrically removed, or any combination of these,among others. In a specific embodiment, the absorber layer made ofcopper indium disulfide is about 1 to 10 microns, but can be others. Ofcourse, there can be other variations, modifications, and alternatives.

The copper indium disulfide material 1360 formed at previous processescan have a p-type semiconductor characteristic through a proper impuritydoping. For example, the copper indium disulfide material 1360 can betransformed to a photovoltaic absorber layer by doping sodium, boron,aluminum impurity materials. The grain of the film assisted by the dopedimpurity material can include substantially a crystallographicchalcogenide structure, which in general belongs to a chalcopyritestructure characterized by properties with excellent photoelectricconversion efficiency. In an embodiment, the copper indium disulfidematerial based photovoltaic absorber layer formed at previous processescan have a p-type semiconductor characteristic. In another embodiment,the copper indium disulfide material based photovoltaic absorber layeris subjected to additional doping process to have certain region withp⁺⁺ characteristic therein for the purpose of forming a high efficiencythin film photovoltaic modules. In an example, the copper indiumdisulfide material 1360 is mixed with a copper indium aluminum disulfidematerial. Of course, there can be other variations, modifications, andalternatives.

Subsequently as shown in FIG. 15, a window layer 1510 is formedoverlying the p-type copper indium disulfide material 1360. The windowlayer 1510 can be selected from a group of materials consisting of acadmium sulfide (CdS), a zinc sulfide (ZnS), zinc selenium (ZnSe), zincoxide (ZnO), zinc magnesium oxide (ZnMgO), or others and may be dopedwith impurities for conductivity, e.g., n⁺ type. The window layer 1510is intended to serve another part of a PN junction associated with aphotovoltaic cell. Therefore, the window layer 1510, during or after itsformation, is heavily doped to form a n⁺-type semiconductor layer. Inone example, indium species are used as the doping material to causeformation of the n⁺-type characteristic associated with the window layer1510. In another example, the doping process is performed using suitableconditions. In a specific embodiment, ZnO window layer that is dopedwith aluminum can range from about 200 to 500 nanometers. Of course,there can be other variations, modifications, and alternative

As shown in FIG. 16, a conductive layer 1530 is added at least partiallyon top of the window layer 1510 to form a top electrode layer for thephotovoltaic module. In one embodiment, the conductive layer 1530 is atransparent conductive oxide TCO layer. For example, TCO can be selectedfrom a group consisting of In₂O₃:Sn (ITO), ZnO:Al (AZO), SnO₂:F (TFO),and can be others. In another embodiment, the formation of the TCO layeris followed a certain predetermined pattern for effectively carried outthe function of top electrode layer for the photovoltaic module withconsiderations of maximizing the efficiency of the thin film basedphotovoltaic modules. In a specific embodiment, the TCO can also act asa window layer, which essentially eliminates a separate window layer. Ofcourse there can be other variations, modifications, and alternatives.

Although the above has been illustrated according to specificembodiments, there can be other modifications, alternatives, andvariations. It is understood that the examples and embodiments describedherein are for illustrative purposes only and that various modificationsor changes in light thereof will be suggested to persons skilled in theart and are to be included within the spirit and purview of thisapplication and scope of the appended claims.

What is claimed is:
 1. A method of manufacturing thin film photovoltaicdevices, the method comprising: accessing a substrate housed in a loadlock station that has been depressurized from an external ambientpressure to a first internal pressure that is less than the externalambient pressure; transferring the substrate from the load lock stationto a first process station, wherein the substrate is transferred to thefirst process station via a first transfer station, the first transferstation is mechanically coupled with the load lock station at a firstend of the first transfer station, and the first transfer station ismechanically coupled with the first process station at a second end ofthe first transfer station; performing a first process for forming athin film photovoltaic device in the first process station, wherein afirst process temperature in the first process station is adjusted usinga first process station temperature system, and a first process pressurein the first process station is adjusted using a first process stationpressure system; returning the substrate from the first process stationto the load lock station via the first transfer station; transferringthe substrate from the load lock station to a second process station,wherein the substrate is transferred to the second process station via asecond transfer station, the second transfer station is mechanicallycoupled with the load lock station at a first end of the second transferstation, and the second transfer station is mechanically coupled withthe second process station at a second end of the second transferstation; and performing a second process for forming the thin filmphotovoltaic device in the second process station, wherein a secondprocess temperature in the second process station is adjusted using asecond process station temperature system, and a second process pressurein the second process station is adjusted using a second process stationpressure system.
 2. The method of claim 1, wherein the first transferstation includes a first transfer station pressure system that maintainsa first transfer pressure during the transferring of the substrate tothe first process station that is equal to the first process pressure.3. The method of claim 1, wherein the first transfer station includes afirst transfer station gas delivery system that delivers an inert gas tothe first transfer station and maintains an inert environment in thefirst transfer station during the transferring of the substrate to thefirst process station.
 4. The method of claim 1, wherein the firstprocess for forming the thin film photovoltaic device comprises filmdeposition, patterning, etching, curing, annealing, or cleaning.
 5. Themethod of claim 1, further comprising, prior to transferring thesubstrate from the load lock station to the second process station,adjusting the load lock pressure from the first internal pressure to asecond internal pressure that is equal to the second process pressure,and wherein the second transfer station includes a second transferstation pressure system that maintains a second transfer pressure duringthe transferring of the substrate to the second process station that isequal to the second process pressure.
 6. The method of claim 1, furthercomprising: transferring the substrate from the load lock station to athird process station, wherein the substrate is transferred to the thirdprocess station via a third transfer station, the third transfer stationis mechanically coupled with the load lock station at a first end of thethird transfer station, and the third transfer station is mechanicallycoupled with the third process station at a second end of the thirdtransfer station; performing a third process for forming the thin filmphotovoltaic device in the third process station, wherein a thirdprocess temperature in the third process station is adjusted using athird process station temperature system, and a third process pressurein the third process station is adjusted using a third process stationpressure system.
 7. The method of claim 6, further comprising, prior totransferring the substrate from the load lock station to the thirdprocess station, adjusting a load lock pressure of the load lock stationfrom the second process pressure to a third internal pressure that isequal to the third process pressure, and wherein the third transferstation includes a third transfer station pressure system that maintainsa third transfer pressure during the transferring of the substrate tothe third process station that is equal to the third process pressure.8. The method of claim 7, wherein one of the first process station, thesecond process station, or the third process station is configured toform a copper-indium composite material with a Cu-rich stoichiometryoverlying an electrode layer on the substrate.